Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a nacelle rotatably supported on the tower, a generator and gearbox housed in the nacelle, and a rotatable hub having one more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles, and transmit the kinetic energy through rotational energy to turn a shaft that couples the rotor blades to the gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid. With the growing interest in wind-generated electricity, considerable efforts have been made to develop wind turbines that are reliable and efficient.
A wind turbine comprises several mechanical and electrical components that generate heat energy losses during their operation. These components include, for example, the gearbox (if provided) and generator that are typically housed in the nacelle. Other heat-generating components may be housed in the tower. For example, a converter and a transformer are typically located in the tower and are utilized to feed electrical energy converted from the mechanical energy of the rotor via the generator into the grid. In addition, one or more controllers for controlling operation of the wind turbine are typically arranged within the tower.
Due to the increased performance and size of modern wind turbines, effective cooling of the above-mentioned components is increasingly difficult, particularly with respect to the heat-generating components within the tower. For example, it has been estimated that for a converter control system operating in a 1.5 MW turbine, about 20 kW is dissipated in heat by the converter. Placement of the converter within the turbine tower without adequate cooling can result in a significant temperature rise within the tower, which may be detrimental to the control system and other components within the tower.
Typically, the heat-generating components in the tower are arranged within a cooling airstream generated by fans. The components may include a heat exchanger that collects the generated heat, with the heat exchanger placed directly in the airstream. The heated air rises in the tower and is typically exhausted through vents near the top of the tower. The tower may include additional vents, for example in the tower entry door, to allow the passage of outside air into the lower portion of the tower. However, even with this type of arrangement, it is often difficult to feed enough external air into the tower for sufficient cooling of the components.
Further, rejecting waste heat from the power components using current cooling systems and methods is expensive. In addition, restrictions on tower cooling may also result from geographic location of the wind turbines. For example, offshore and near-shore sites generally do not rely on external air as a cooling medium due to the high salt content and humidity of the air, which would result in a corrosive environment within the tower. These sites use an isolated cooling system, such as an air conditioning system with a heat exchanger. A dehumidifier may also be utilized. Humidity and external temperature are considerations that may significantly limit the available cooling options in a given geographical location.
In other areas of technology, such as computer processing, various cooling techniques utilize cooling fluids to cool electrical components of the system. For example, the electrical components of the computer are submerged in an immersion cooling bath so that the system maintains a suitable operating temperature. Such systems, however, are much smaller than wind turbine systems, operate at a much lower voltage (e.g. 5, 12, or 15 VDC as compared to 1300 VDC and/or 120 or 230 VAC as compared to 690 VAC), are typically located indoors where air conditioning units are present, and are not limited to certain space limitations (i.e. within the wind turbine tower or nacelle).
Accordingly, there exists a need for an improved system and method for cooling electrical components of the power converter of the wind turbine that takes into account the design considerations above. More specifically, a system and method that utilizes an immersion cooling bath to cool such components during operation, thereby eliminating the need for fans and/or air conditioning units would be advantageous.